Organ formation is a fundamental aspect of animal embryogenesis that is known to require the coordinated development of cells as groups. However, relatively little is known about the molecules or mechanisms that underly organ formation. In order to gain insight into these processes we are studying the development of the C. elegans pharynx, a complex neuromuscular organ required for nematode feeding. In particular, we are studying a novel transcription factor, called peb-1, which was identified through its ability to bind a pharyngeal-organ-specific enhancer element. Preliminary results suggest that peb-1 is involved in generating cell-type diversity in the pharyngeal primordium, a step during organogenesis which is poorly uncharacterized. We plan to determine the function of peb-1 during pharyngeal development using three experimental approaches: characterizing peb-1's expression pattern, analyzing the effects of misexpressing peb-1 outside the pharynx, and characterizing the phenotype of a peb-1 loss-of-function mutant. Insight gained in our studies should translate into a better understanding of vertebrate organogenesis, particularly for the heart. In addition, our studies may reveal insight that can be applied to the development of clinical therapies using human embryonic stem cells.